Selective conversion of alcohols in water to carboxylic acids by in situ generated ruthenium trans dihydrido carbonyl PNP complexes

Abstract

In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process.

Acceptorless dehydrogenative coupling of alcohols catalysed by ruthenium PNP complexes: Influence of catalyst structure and of hydrogen mass transfer

“…at room temperature or at 80°C in C 6 D 6 did not give rise neither to the formation of any new complex nor to alcohol-derived reaction products. Interestingly, this complex was successfully used in primary alcohol oxidation into the corresponding acid, though with a significantly lesser activity than derivatives featuring less bulky substituents on the phosphorous centers, which tends to indicate that too high steric protection is detrimental to the catalytic activity [26,33]. Finally, in order to compare our results with those of other commercially available ruthenium catalysts active in the absence of a base, we probed Milstein's catalyst's (13), C12-N1-Ru1 = 123.24(11).…”

“…This compound was prepared similarly to 3b by using Ru-MACHO 1c (250 mg, 0.42 mmol) instead of complex 1b with a larger amount of solvent (40 mL This species was previously prepared by Prechtl and coworkers by treating RuH (H 2 )[N(C 2 H 4 PtBu 2 ) 2 ] with a primary alcohol [26]. We describe herein an alternative procedure.…”

“…Applying the same reaction conditions to 1d leads to the known amido monohydride 4 instead of the targeted bishydride 3d [26]. The solid-state structure of this compound was determined using X-ray diffraction (Fig.…”

Reactions in Water – A Greener Approach Using Ruthenium Catalysts

“…However alternatively the “aldehyde‐water shift” reaction, (Figure a) in which the aldehyde is oxidized by water into carboxylic acid with the concomitant release of hydrogen gas is a much greener approach. In recent years, the dehydrogenation of alcohols to carboxylic acids, worked by Milstein, Grützmacher, and Prechtl proposed the AWS as an intermediate reaction step involving dehydrogenation of a hydrated aldehyde (geminal‐diol). Computational studies further supported the potential use of water as an oxidant for aldehydes.…”

Light driven styrene epoxidation and hydrogen generation using H2O as an oxygen source in a photoelectrosynthesis cell

“…The employment of hydrogen peroxide is an attractive option both on environmental and economic grounds [4][5][6][7] giving just water as a byproduct. Another option is to use water as the source of oxygen for the epoxidation reaction with the formation of hydrogen as a valuable side product as indicated in the equation below, 8 which involves the input of 37.35 Kcal mol -1 given its uphill thermodynamics that can be provided thermically 9,10 or photochemically 11 with sunlight. This strategy also benefits from the formation of hydrogen as a byproduct that is also a clean energy vector.…”